SS 433 (or V1343 Aql) is a fascinating interacting binary system.
It is currently believed to consist of an A-type supergiant star
approximately 27 times the diameter of the Sun and a black hole.
The star and black hole orbit one another in just over thirteen days.
At this close proximity, the black hole in the system is pulling material
from the supergiant star. This material circles the black hole forming
a large disk of gas. Some of this material eventually falls into the
black hole, other material is blown away from the disk in large "winds",
and the remaining material is ejected perpendicular to the disk
as very narrow "jets". The material in these jets is travelling at
0.26c, or 26% the speed of light!

My recent work along with a collaboration at
Georgia State University and
in the Netherlands, identified the supergiant star in SS 433
as well as determining that its companion is most likely a black hole.
Our work was highlighted in the May 2004 issue of Sky and Telescope
magazine (p 16).
We are continuing our studies of SS 433 and have
joined with two additional teams who are studying SS 433 in x-ray
and radio wavelengths. We are in the process of analyzing data from
coordinated simultaneous observations
of SS 433 in 2005 using x-ray, radio, infrared, and optical observatories!

Planetary Nebula Central Stars are the focus of another
project. I have been observing these stars for several years in
an attempt to find binary central stars. The central stars are
remnants of sunlike stars which have shed their outer envelopes.
These envelopes are blown away from the star and appear to us as
planetary nebulae. Many planetary nebulae have very complex shapes
and we are unsure what creates the varied and fascinating
structures we observe. One possibility is that there is a companion
to the central star and that the orbit of these stars creates the
physical conditions which shape the outflowing gas. My research
has been focused on determining how many and specifically which
planetary nebulae have binary central stars. Primarily this has
been done by searching for specific brightness variations which
are caused by close or interacting binary stars.

Close Binary Stars:

O-type stars are the most massive stars known. Unfortunately
we do not know precisely what masses they do have. In
collaboration with Doug Gies
at Georgia State University
I have been surveying groups of O-type stars to search for binary
systems. The only way for us to directly determine a star's mass is
if it has a companion. The specific orbital speed and the distance
between the stars can tell us what the mass of each star is. The
frequency of stars that are binaries can also tell us much about how
the stars formed, and important issue in understanding our Universe.
We have been using the spectrum of these stars to find binary systems
and to determine the orbital periods.

Circumstellar Nebulosity:

The structure of nova shells was the topic of my
doctoral dissertation. Nova shells are created by material being
blown off the surface of a white dwarf star in a close binary
system known as a cataclysmic variable. The white dwarf in the
system is surrounded by an accretion disk. The gas in the disk
eventually falls to the surface of the white dwarf and eventually
the white dwarf undergoes a thermonuclear runaway on its surface.
This ejects the material which is seen as the nova shell. My
work used spectra of the different portions of nova shells to
determine the shape and expansion speed of the shell. This
information can help us more aaccurately understand the processes
occuring during the thermonuclear runaway.